Reversible galvanic battery.



No. 678,722. Patented July !6, I901.

T. A. amsouq REVERSIBLE GALVANIC BATTERY.

(Application filed June 20, 1901.)-

Inventar ,4 M M W080 cooooouomooooccoo m on o0 (No Model.)

Witnesses ,4. a

Att'ys.

m: wimp an; co. PNOTOLITNDH msnmoron. a. c

mares arnnr @rrrcn.

THOMAS A. EDISON, OF LLEWELLYN PARK, NEW JERSEY.

REVERSIBLE GALVANIC BATTERY.

SPECIFIGATION forming part of Letters Patent No. 678,722, dated July 16,1901.

Original application filed March 1, 1901, Serial No. 49,453. Divided andthis application filed June 2 0, 1901. Serial 110.65.284. (No model.)

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, a citizen of the United States,residing at Llewellyn Park, in the county of Essex and State of NewJersey, have invented a certain new and useful Improvement in ReversibleGalvanic Batteries, (Case No. 1,060,) of which the following is aspecification.

My invention relates to improvements in reversible or so-called storagebatteries; and my object is to produce a reversible galvanic cell ofgreat permanency and of remarkably light weight per unit of energy.

In my application for Letters Patent, filed October 31, 1900, Serial No.34,994, I describe an improved reversible galvanic cell wherein themetals, cadmium, and copper are employed as the elements in an alkalineelectrolyte and by means of which I secured a very permanent cell, onewherein the initial and finalstates of the electrolyte are the same,and, finally, one which was capable of storing a greater amount ofenergy per pound of cell than batteries commercially used before thattime for the same degree of durability. My present invention is designedto further lighten the weight of the cell in comparison to the storedenergy and to deliver the energy to the exterior circuit at a higherrate.

In the alkaline zincate type of battery as commercially used, so far asI know, copper oxid has heretofore been used exclusively as theoxygen-furnishing element when the battery is discharged, the copperbeing reduced to the metallic state. The only other elements which havebeen suggested and would be available as substitutes for copper in thesebatteries have been these lower in the electrolytic series, such asmercury and silver; but so far as I know these metals have not beensatisfactorily or commercially utilized ments for an element or compoundcapable of being used in an alkaline electrolyte, the

l heat of formation of whose oxid should be as low or lower than that ofoxid of mercury, and in this I have been successful, the result beingthe discovery of an element for furnishing the oxygen to the oxidizableelement on discharge with even greater freedom that? oxid of mercury,while at the same time the new element is less expensive,is of lessweight, is of greater permanency, and finally is of greaterinsolubilityin the electrolyte. I have also sought by experiment for anelement superior to cadmium as the oxidizable element on discharge, withthe object in View of further reducing the weight and cost of the cell,and I have discovered an element for the purpose possessing thesedesirable characteristics. As a result a reversible galvanic cellequipped with the new elements is of great permanence, is relativelylight and inexpensive, and is of great power.

The elements are preferably carried or supported by hollow perforatedplates, forming receptacles or pockets, which are illustrated in theaccompanying drawings, forming part of this specification, and in which-Figure 1 is a face View of one of the plates, having three pockets orreceptacles, showing the front wall partly broken away. Fig. 2 is asection on the line 2 2 of Fig. 1. Fig. 3 is a plan showing two of theplates forming a single combination, and Fig. 4 an enlarged detailsection.

In all of the above views corresponding parts are represented by thesame numerals of reference.

Each plate is formed with two walls 1 and 2, constructed, preferably, ofa single continuous sheet, made, preferably, of very thinsheetnickel-say about .005 of an inch in thicknessand bent at its bottomaround a horizontal frame 3, from which extend the verticalspacing-frames 4 4, to all of which frames the sheet is secured by meansof nickel rivets, as shown, to form a strong rigid hollow plate, withpockets or receptacles be- 5 tween the vertical frames at at. The walls1 and 2 of the plate, as shown, are perforated with small holes arrangedvery closely together and each about .015 of an inch in diameter. Iprefer to use nickel in the construction of the plates, since that metalis not oxidizable by electric oxidation in an alkaline solution. Iron,on the other hand, is slightly oxidized under these conditions and isnot so desirable; but if very carefully and perfectly plated with nickelit may be used satisfactorily for the construction of either the platesor the frames. Obviously the frames 3 and 4 may be, and in someinstances preferably are, constructed of hard rubber or other inertmaterial, to which the perforated sheet is riveted, as explained.Secured to one or both of the sides of the plate are a number ofinsulated spacing-blocks 5 5 to prevent adjacent plates from touchingwhen immersed in the electrolyte.

In the manufacture of my new oxidizable element for use in a reversiblegalvanic cell I first preferably take monosulfid of iron and reduce itby a crushing operation until the particles thereof may be passedthrough a 'screen having about forty thousand openings per square inch,and I intimately mix about eight parts, by weight, of the powderedmonosulfid with about two parts, by weight, of flake graphite of a sizeconsiderably larger than the perforations in the walls of the pockets orreceptacles. Flake graphite being exceedingly thin and of large areagives an extensive conducting-surface in proportion to its bulk andweight. This mixture is then moistened with a twenty-per-cent. solutionof potassic hydroxid, and the dampened mass is packed into the pocketsor receptacles of the proper plates by a suitable tamping tool. Owing tothe want of flexibility of the graphite, the mixture packs to a hardporous mass:

The effect of electrolytic gasing therefore does not disintegrate themass as. awhole whenproperlycomprcssed. Aftereachpocket or receptaclehas been tightly packed with the massalmost to its top a wad of asbestosfiber 6, about a quarter of an inch in thickness, is introduced into thepocket or receptacle above the mass, and on top of this packing isplaced a strip of sheet-nickel 7, entirely covering the asbestos andfilling the mouth of the pocket, which strip is permanently secured inposition by nickel wires 8, threaded through the openings near the topof the pocket, as shown particularlyin Fig. 2. The element thus formedis subjected to electrolytic oxidization in asolution of potassichydroxid, whereby sulfur will be set free and combining with the alkaliforms a sulfid of potassium, which diffuses out of the mass, while theiron is converted to a ferrous oxid thereof. This diffusion of thealkaline sulfid out of the plate is hastened and facilitatedbysubjecting the contents of the plate to alternate oxidization andreduction by alternately reversing the oxidizing-current, and by severalof these operations the whole of the sulfur will be eliminated and theelement will be ready for use after the iron has been reduced to themetallic state. Since iron eme e does not decompose water, there willobviously be no local action between it and the graphite. The oxidformed from the sulfid increases in bulk and being intermediately mixedwith the graphite produces considerable pressure on the walls of theplate, which prevents any disturbance of the initial state of the masseven when it is subjected to strong gasing within the pores byovercharging the element electrically. The object of using themonosulfid is to secure the greatest amount of iron oxid in the smallestspace and in a form capable of being reduced to the metallic stateelectrolytically.

My attempts to utilize iron as the oxidizable element in an alkalinereversible battery were for a long time frustrated by the facts,determined only after exhaustive experiments, that dried oxids of ironwere not reducible to any extent by the current; that spongy ironreduced by hydrogen from different iron salts was not oxidizable to anyconsiderable extent by the current; that the hydrates of iron were verybulky and difficult of use Without drying, which operation effected someobscure change therein to render them nearly inert in the presence ofthe reducing current; that bulky ferric oxid was not capable of anyconsiderable reduction by the current, and, finally, that ferrous oxid,though easily reducible, was very difficult to prepare on account ofatmospheric oxidation. The formation of the ferrous oxid, in the firstinstance, within the pockets or receptacles did away with the objectionsdue to the bulk of the hydrates, while the oxid thus formed "isperfectly reducible by the current. In stead of forming the oxid in thisway by oxidizing the monosulfid in an alkaline solution, it will beobvious that salts of iron, like ferrous chlorid, may be packed with thegraphite and when placed in an alkaline solution form chlorid of thealkali and ferrous oxid of iron, the alkaline chlorid diffusing out ofthe mass. The results, however, are not so good as when the sulfid ofiron is used,since the quantity of finely-divided iron produced therebyis considerably less and is also less porous, offering, therefore, areduced opportunity for the solution to penetrate the mass and loweringin consequence its currentconducting capacity. Metallic iron, even whenfinely divided, as produced by electrolytic reduction, does not ofitself oxidize in solutions of the fixed alkalies, and the oxid of ironis not appreciably soluble. Compact, dense, or non-porous iron-i. 6.,iron having relatively large particles-when subjected to a powerfuleloctrolytic oxidation forms a small quantity of a soluble ferrate ofthe alkali and dissolves in the electrolyte. On the other hand, finelydivided iron obtained as described when subjeeted to electrolyticoxidation does not form a soluble ferrate, butis converted into theinsoluble ferrous oxid.

My improved oxidizable element is therefore IIO craves absolutelypermanent, so that in the operation of the battery the electrolyte isnot changed at any stage of the working, and absolutely no deteriorationof the iron element takes place.

Having described the ad vantages and char acteristics of and thepreferred manner of making the oxidizable element, reference will now bemade to the preferred oxygen f urnishing or storing element of the cell.

1 have discovered by experiment that the lower oxids of nickel andcobalt when in contact with aconductor in an alkaline solution can bealmost wholly raised from this lower to a higher stage of oxidationelectrolytically than is possible by chemical means and that thesehigher oxids revert to a lower stage by reduction with extreme case, andavailing myself of this fact Ihave constructed an oxygen-storingelementcapable of great capacity, of light Weight, and of high permanence.Neither the oxid of nickel nor of cobalt is appreciably soluble in analkaline electrolyte, and both nickel and cobalt give nearly the samevoltage in use; but since nickel is less expensive than cobalt I preferto use the former element for the purpose.

The preferred process of in akingthe oxygen storing element consistsinfirst precipitating either the monoxid or black hydrated dioxid of themetal-say nickel-in the usual way, washing the precipitate free from theproducts of the reaction, filtering off the liquid, and drying off theprecipitate. .The resulting dried hydrated oxid is then powdered veryfine and is ready for use. Either oxid may be used with the sameresults. The process above outlined applies to cobalt as Well as tonickel. About seven parts, by Weight, of the finely-powdered hydrate andthree parts, by weight, of flake graphite are then intimately mixed andmoistened with a small quantity of a strong solution of potassichydroxid, so as to dampen the mass, which is then inserted in thepockets or receptacles of the proper plates in small quantities at atime and thoroughly tamped at each accession. Finally the mass iscovered with a layer of asbestos, held in place by a plate of nickelsecured in position by nickel wires, as I have described in explainingthe make-up of the oxidizable element. The plates the pockets of whichare thus supplied with the mixture of the hydrated oxid and graphite arethen immersed in a solution of potassic hydroxid in water and subjectedfor a considerable time to an oxidizing-current of about fiftymilliamperes per square inch of surface, during which the oxid is eitherraised to a higher stage of oxidation than the black oxid (Ni O or elseacts as an absorber of oxygen in some manner unknown to me. .Vhateverthe action may be, the oxid so treated acts as a most efficientoxygenstoring element for commercial use in a galvanic battery.

The object of employing graphite, Whichis not affected by electrolyticoxidation, is to tance from the contact-surfacethan the thickness of asingle particle of the powdered oxid. Furthermore, there is no localaction between the nickel or cobalt oxide and the graphite.

The reason why nickel hydrate is preferably used instead of othercompounds of nickel is that the metal itself when finally divided (asobtained by reducing a nickel compound by hydrogen or electrolysis) isnot oxidizable to any considerable extent when subjected to electrolyticoxidation in an alkaline solution. The sullid of nickel is notdecomposed by electrolysis under the conditions of battery-work, and thesullid of co halt only imperfectly. Hence the hydrates are the mostavailable compounds for use, since they do notbecome inert to the sameextent as hydrates of the oxids of iron after drying, they are easilyprepared, and by absorbing the solution they swell within the pockets orreceptacles, so as to insure intimate con tact and stability. During thecharging of the cell the absorption of oxygen by the oxid of nickel orcobalt causes the oxid to further swell and bulge the pockets orreceptacles outwardly, and on discharge a proportionate contractiontakes place. in order that the walls of the pockets or receptacles mayal- Ways maintain the desirable intimate contact with the activematerial, the pockets are, as stated, made of some highly-elastic metal,such as hard-rolled sheet-nickel, so that at each contraction of themass the pocket-walls will by their elasticity keep in contacttherewith.

Having constructed the two elements of the battery as above explained,they are preferably utilized together in a solution of twentyfive percent. of pot-assic hydroxid in water and the cell is ready for use, andwhen charged the iron is in the metallic form and the nickel or cobaltoxid is raised to the superperoxid stage described.

Owing to several obscure reactions which take place when the battery isdischarged, and also to a change of resistance within the electrodes,the voltage is variable; but the average voltage over the wholedischarge is about one volt, rising as high as 1.32 volts, and scmetimes higher, when freshly charged.

My improved battery can be overcharged, fully discharged, or evenreversed and charged in the opposite direction without any injury.Overgassing does not disturb the initial state of the materials in thepockets,

all the ingredients are insoluble, the supporting-plates are unattackedby electrolytic oxidation, and the whole operation is independent of thestrength of the solution, so that the battery is of great permanence,while at the same time more energy will be stored per unit of weightthan with any permanent practical combination heretofore suggested.

I have constructed a battery as above described which gives an availablestorage capacity of one-horse-power hour for seventythree pounds weight;but it may be made lighter without destroying its permanent character.

The specific magnetic metals are iron, nickel, and cobalt. By theexpression oxid of a specific magnetic metal other than iron as employedin my claims I mean oxid of nickel, oxid of cobalt, or a combination ofsuch oxids. By the use of that expression it is my purpose to embraceand include generically both of these utilized oxids.

I do not claim herein the new depolarizer per se comprising anelectrolytically-active oxid of nickel or cobalt, nor do I claim herein,broadly, such depolarizer when used in a battery of the improved typeinvented by me, wherein the electrolyte remains unchanged at all timesand wherein both the active materials are insoluble in all conditions ofuse, nor do I claim herein such a depolarizer, broadly, in combinationwith any suitable oxidizable materials. In my present application Iclaimthenew oxidizable elementper se and in combination with the newdepolarizer. Claims, first, on the new depolarizerper so," secondly, onsuch depolarizer when used in a battery of the new type invented by me,and, finally, on such depolarizer in combination with any suitableoxidizable element are made in my application for Letters Patent filedon even date herewith (Case No. 1,061) as a division of my applicationfiled March 1, 1901, Serial No. 49,453, of which the present case isalso a division. Claims on an electrolytically-active oxid of cobaltused as a depolarizer are made in my application filed March 1, 1901,

Serial No. 49,452.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is as follows:

1. An active oxidizable element for an alkaline reversible galvanicbattery, comprising a conducting-support and electrolyticallyactive,finely-divided iron carried thereby and capable of being oxidized ondischarging, substantially as set forth.

2. An active oxidizable element for a reversible galvanic battery,comprising a conducting-support and a mixture of flake-like inertconducting material and electrolytically-active, finely-divided ironcarried thereby capable of being oxidized on discharging,

substantially as set forth.

3. An active oxidizable element for a reducting-support and a mixture offlake-graphite and electrolyticallyactive, finely-divided iron carriedthereby capable of being oxidized on discharging, substantially as setforth.

4:- An active deoxidizable element for an alkaline reversible galvanicbattery, comprising a conducting-support and finely-divided ferrous oxidcarried thereby and capable of being deoxidized on charging,substantially as set forth.

5. An active deoxidizable element fora reversible galvanic battery,comprising a con ducting-support and a mixture of flake-like inertconducting material and finely-divided ferrous oxid carried therebycapable of being deoxidized on charging, substantially as set forth.

6. An active deoxidizable element for a reversible galvanic battery,comprising a con ducting-support and a mixture of flake-graphite andfinely-divided ferrous oxid carried thereby capable of being deoxidizedon charging, substantially as set forth.

7. An active deoxidizable element for an alkaline reversible galvanicbattery, comprising a conducting-support and an oxid of iron carriedthereby electrolytically reducible to the metallic state upon charging,substantially as set forth.

8. An active deoxidizable element for a reversible galvanic battery,comprising a conducting-support and a mixture of flake-like inertconducting material and an oxid of iron carried therebyelectrolyticallyreducible to the metallic state upon charging, substantially as setforth.

9. An active deoxidizable element for a reversible galvanic battery,comprising a conducting-support and a mixture of flake-graph.- ite andan oxid of iron carried thereby electrolytically reducible to themetallic state upon charging, substantially as set forth.

10. In a reversible galvanic battery,the combination of an electrolytewhich remains unchanged during all conditions of working, and twoelements therein insoluble in such electrolyte, the oxidizable elementhaving forits active material electrolytically-active, finelydividediron, substantially as set forth.

11. In a-reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, andanother conducting-support carrying an oxid of a specific magnetic metalother than iron andcapable of furnishing oxygen for the oxidation of theiron on discharge, substantially as set forth.

12. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carryingfinely-divided oxid of iron when discharged,and another conducting-support carrying an oxid of a specific magneticmetal.

other than iron and capable of storing oxygen on charging, substantiallyas set forth.

13. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, an-

IIO

wares other conducting-support carrying an oxid of a specific magneticmetal other than iron and capable of furnishing oxygen for the oxidationofthe iron on discharge, and an inert conducting material intimatelymixed with said oxid, substantially as set forth.

1 1. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, anotherconducting-support carrying an oxid of a specific magnetic metal otherthan iron and capable of furnishing oxygen for the oxidation of the ironon discharge, and flake-graphite intimately mixed with said oxid,substantially as set forth.

15. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, an inertconducting material intimately mixed wit-l1 said finely-divided iron,another conducting-support carrying an oxid of a specific magnetic metalother than iron capable of furnishing oxygen for the oxidation of theiron on discharge, and an inert conducting material mixed with saidoxid, substantially as set forth.

16. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged,flakegraphite intimately mixed with said finelydivided iron, anothereonductingsupport carrying an oxid of a specific magnetic metal otherthan iron capable of furnishing oxygen for the oxidation of the iron ondischarge and flake-graphite mixed with said oxid, substantially as setforth.

17. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, andanother conducting-support carrying oxid of nickel capable of furnishingoxygen for the oxidation of the iron'on discharge, substantiallyas setforth.

18. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided oxid of iron whendischarged,and another conducting-support earrying an oxid of nickel,substantially as set I forth.

19. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, andanother conducting-support carrying oxid of nickel having when chargedelectrolytically more oxygen than M 0 substantially as set forth.

20. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, andanother conducting-support carrying a by drated oxid of nickel,substantially as set forth.

21. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, a11- otherconducting-support carrying oxid of nickel capable of furnishing oxygenfor the oxidation of the iron on discharge, and flakegraphite intimatelymixed with said oxid, substantially as set forth.

22. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided oxid of iron when discharged,another conducting-support carrying an oxid of nickel, andflake-graphite intimately mixed with said oxid, substantially as setforth.

23. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided iron when charged, anotherconducting-snpport carrying oxid of nickel having when chargedelectrolytically more oxygen than Ni O and flake-graphite intimatelymixed with said oxid, substan stantially as set forth.

24:. In a reversible galvanic battery, an alkaline electrolyte, acondnoting-support carrying finely-divided iron when charged, an othercond uctin g-support carrying a hydrated oxid of nickel, andflake-graphite intimately mixed with said oxid, substantially as setforth.

. 25. In a reversible galvanic battery, an al-' kaline electrolyte, aconducting-support car rying finely-divided iron when charged, anotherconducting-support comprising areceptacle having elastic walls, and anoxid of a specific magnetic metal other than iron carried within saidreceptacle and engaged by the walls thereof with an elastic pressure,said oxid being capable of furnishing oxygen for the oxidation of theiron on discharge,snb stantially as set forth.

26. In a reversible galvanic battery, an alkaline electrolyte, aconducting-support carrying finely-divided oxid of iron when discharged,another conducting-support com prising a receptacle having elasticwalls, and an oxid of a specific magnetic metal other than iron carriedwithin said receptacle and engaged by the walls with an elastic pressureand capable of storing oxygen on charging, substantially as set forth.

This specification signed and witnessed this 17th day of June, 1901.

THUS. A. EDl'SONl Witnesses:

FRANK. L. Dvnn, Gnarnnnn J. WILLTAMS,

